Method for controlling and removing solid deposits from a surface of a component of a steam generating system

ABSTRACT

A method for controlling and removing solid deposits from a surface of at least one component of a steam generating system, wherein the solid deposits are formed from an impurity introduced into the steam generating system, is disclosed.

This application is a continuation of application Ser. No. 08/570,799,filed Dec. 12, 1995, now U.S. Pat. No. 5,779,814, which is acontinuation of U.S. patent application Ser. No. 08/214,927, filed Mar.17, 1994, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method for controlling and removing soliddeposits from a surface of a component of a steam generating system,wherein the solid deposits arise from impurities introduced into thesteam generating system.

2. Brief Description of the Background Art

The fact that various salts are introduced as impurities into steamgenerating systems is well known by those skilled in the art. Forexample, condenser cooling water inleakage may be the greatest or mostcommon source. Impurities may be introduced in the form of chemicaladditives, ion exchange media, welding residuals, grinding operations,desiccants and related construction/maintenance functions. Theseintroduced impurities include, such as for example, but not limited to,calcium, magnesium, sodium, potassium, aluminum, chloride, silica, andsulfate, and insoluble salts such as, for example, but not limited to,calcium sulfate and aluminum silicate. These impurities are commonlyreported as solids in the surface analysis of steam cycle materials.

The role and impact of introduced impurities include variousdebilitating corrosion mechanisms, particularly in the boiler and steamturbine systems. The most common known methods to minimize the effect ofintroduced impurities include exclusion and removal on ion exchangemedia. It is known by those skilled in the art that steam cycles aretreated with alkalizing amines directed at maintaining alkalinity or pHcontrol and reducing agents to promote passivation and minimizecorrosion from impurities inherent in the steam generating system suchas, for example, iron. EPRI, Workshop On Use Of Amines In ConditioningSteam/Water Circuits, "Use Of Amines In Once Through Steam Generators",authored by G. Quadri, et al., Tampa, Fla., U.S.A., September 1990,discloses the use of dimethylamine in utility fossil fueled power plantboilers in connection with the conventional manner of steam cyclealkalization, known by those skilled in the art, to reduce corrosion offerrous materials.

The use of alkalizing amines to minimize corrosion caused by impuritiesinherent to the steam generating system is not generally compatible withthe objective to minimize the formation of solid deposits arising fromimpurities introduced into the steam generating system. For example,maintenance of high alkalinity with alkalizing amines such as, forexample, ammonia, limits monovalent cation such as, for example, sodium,removal on ion exchange systems such as, for example, condensatepolishers. (Salem, E., "Separation Technology Requirements For OperationIn The Amine Cycle With Deep Bed Condensate Polishing", fromproceedings, workshop on Use Of Amines In Conditioning Steam/WaterCircuits, EPRI, Tampa, Fla. September 1990). Therefore, it is oftennecessary to make a compromise between these two objectives. Prior tothe instant invention, attempts to achieve both objectives wereeconomically unattractive since the ion exchange system service life wasshortened.

The literature clearly establishes the effect of introduced impuritieson various corrosion processes or mechanisms. For example, caustic oracid forming species can preclude protective oxide stability, leading tocatastrophic failure of materials, including corrosion resistant alloys.These materials are used in critical applications including steamgenerator tubing that provides the safety boundary in design of, such asfor example, nuclear steam generators. The solid deposits that arisefrom impurities introduced into the steam generating system precipitateon the surfaces of the steam generating system forming scale. Theaccumulation of these solid deposits and scale prevents effective heattransfer, interferes with fluid flow of the water carrying system, andfacilitates corrosive processes. These solid deposits formed byimpurities introduced into the steam generating system is an expensiveproblem in many industrial applications such as, for example, theutility power industry, causing delays and shut downs for controllingand removing these solid deposits, and adding to the costs of operatingand maintaining the steam plant operations. More specifically, theseintroduced impurities present similar issues on critical components ofsteam turbines and failures are common to nuclear and fossil fueledpower plants. These failures include, for example, decrease in steampressure and reduction in high pressure turbine output resulting in adecrease in energy output of the power plant, and turbine corrosion.Further, stress corrosion failures are common on turbine components andare caused, in part, by steam formed deposits including, for example,introduced impurities.

It is well known to those skilled in the art that the electrophoreticproperties of steam formed solid deposits are typically not neutral.These deposits exhibit acid and base centres which give rise tocatalytic properties and to selectivity for sorption of soluble ionssuch as, for example, Na⁺ and Cl⁻. Solids in alkaline systems usuallyexhibit acidity while those in acidic systems exhibit base properties.Further, some solid deposits such as, for example, alumina silicates,are known to exhibit bifunctional properties.

The acid strength and capacity of these solid deposits such as, forexample, Al₂ O₃ and SiO₂, are influenced by many factors including themolar ratio such as, for example, between alumina and silica, by thetemperature at which the solid deposit is formed, by stress inducedcrystalline imperfections and by gamma irradiation.

It will be appreciated by those skilled in the art that the abovementioned background art does not teach or suggest the method ofcontrolling and removing from the surface of a component of a steamgenerating system solid deposits formed from an impurity introduced intothe steam generating system. Therefore, it will be understood by thoseskilled in the art that applicants have discovered unexpectedly that themethod of the present invention comprising adding to an aqueous phase ofa steam generating system an effective amount of at least one volatileamine having a pKa value greater than about 10.61 and providing thermalcycling results in controlling and removing solid deposits from thesurface of a component of the steam generating system that are superiorto results of others previously achieved.

In spite of this background material, there remains a very real andsubstantial need for a method of controlling and/or removing soliddeposits arising from introduced impurities from the surface of acomponent of a steam generating system.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the Electron Dispersive Spectroscopy spectra for solid aciddeposits collected by sampling during initial dimethylamine additionemploying the method of the instant invention.

FIG. 2 compares the steam generator average sodium concentration inrelation to initial dimethylamine addition employing the method of theinstant invention.

FIG. 3 compares the steam generator average sodium concentration inrelation to second phase testing of dimethylamine addition employing themethod of the instant invention.

FIG. 4 compares the steam generator average sulfate concentration inrelation to initial dimethylamine addition employing the method of theinstant invention.

FIG. 5 compares the steam generator average sulfate concentration inrelation to second phase testing of dimethylamine addition employing themethod of the instant invention.

FIG. 6 shows turbine and steam drum sample deposit analyses, prior toemploying the method of the instant invention.

FIGS. 7 through 11 show the particulate, anion and cation fractions ofaluminum, silica, calcium, potassium, and sodium, respectively, removedfrom a boiler drum sample for baseline conditions and upon employing themethod of the instant invention.

FIG. 12A shows the Electron Dispersive Spectroscopy spectra forestablishing a baseline for economizer inlet samples.

FIGS. 12B and C show the Electron Dispersive Spectroscopy spectra forsamples at the economizer inlet for cleanup cycles employing the methodof the instant invention.

FIG. 12D shows the Electron Dispersive Spectroscopy spectra for a sampleat the boiler drum for cleanup of cycles employing the method of theinstant invention.

FIG. 13 shows the improvement in high and intermediate pressure turbineperformance when employing the method of the instant invention.

SUMMARY OF THE INVENTION

The present invention has met the above-described needs. The presentinvention provides a method for controlling and removing solid depositsfrom a surface of at least one component of a steam generating systemwherein the solid deposits are porous and are formed from an impurityintroduced into the steam generating system which comprises adding to anaqueous phase of the steam generating system an effective amount of atleast one volatile amine having a pKa value greater than about 10.61 andselected from the group consisting of an alkyl amine, a cyclo alkylamine, and derivatives thereof, converting the aqueous phase having thevolatile amine to a steam phase having the volatile amine, wherein thesteam phase is selected from the group consisting of wet steam,saturated steam and superheated steam, exposing the steam phase havingthe volatile amine to the surface of the component laden with the soliddeposits, wherein each of the solid deposits has at least one functionalsite selected from the group consisting of (1) an acidic site to whichan inorganic cation is sorbed, (2) a basic site to which an inorganicanion is sorbed, and (3) combinations thereof, for effecting selectivesorption of the volatile amine by the solid deposit and displacing theinorganic cation, anion or combinations thereof, and providing thermalcycling having a temperature ranging, for at least one cycle, fromgreater than or equal to 0° C. (Centigrade) to less than or equal toabout 550° C. for effecting at least one cycle of sorption anddesorption of the volatile amine wherein the rate of the desorption ofthe volatile amine exceeds the rate of diffusion of the volatile aminefrom the porous solid deposit for controlling and removing the poroussolid deposits from the surface of the component.

In a preferred embodiment of this invention, the method as describedherein, is provided wherein the volatile amine is dimethylamine.

In another embodiment of this invention, the method, as describedherein, is provided wherein the volatile amine is an amine selected fromthe group selected consisting of mono-N-butylamine, monomethylamine,monoisopropylamine, tri-N-propylamine, monoethylamine, trimethylamine,triethylamine, diisobutylamine, di-N-propylamine, diethylamine,ethyl-N-butylamine, quinuclidene, tetramethyl-imino-bis-propylamine,pyrrolidine, di-N-butylamine, diisopropylamine,dimethylamino-propylamine, N-ethylcyclohexylamine, and 1,5diazabicyclo5.4.0undec-5-ene.

Another embodiment of this invention provides a method, as describedherein, wherein the component of the steam generating system is selectedfrom at least one of the group consisting of a turbine and a steamgenerator, and more preferably wherein the turbine and the steamgenerator are that of a utility power station.

Another embodiment of this invention provides a method for controllingand removing solid deposits from a surface of at least one component ofa steam generating system, as described herein, wherein the removal ofthe solid deposits is carried out on-stream with the steam generatingsystem operational, or optionally the removal of the solid deposits iscarried out off-stream with the steam generating system shut down.

In yet a further embodiment of this invention, the method, as describedherein, is provided including adding to the aqueous phase of the steamgenerating at least one amine having a pKa value less than about 10.61.

In a preferred embodiment of this invention, a method is provided asdescribed herein, including recovering substantially all the megawattsof energy lost due to the accumulation of the solid deposits at thesurface of the turbine.

In another preferred embodiment of this invention, a method is provided,as described herein, including improving the thermal efficiency of thesteam generating system.

DETAILED DESCRIPTION OF THE INVENTION

The instant invention is directed to a method for controlling andremoving solid deposits from a surface of at least one component of asteam generating system wherein the solid deposits are porous and areformed from an impurity introduced into the steam generating system.

As used herein, the term "steam generating system" is meant to includeany type of system containing an aqueous phase that is capable of beingconverted to a steam phase, including but not limited to, for example,industrial boiler water systems, process boiler water systems, andboiler water systems of a utility power station such as, for example,nuclear power plants and fossil fuel power plants. A "component" of thesteam generating system refers to an element making up the steamgenerating system as understood by those skilled in the art and is meantto include, such as for example, but not limited to, a steam generator,a turbine, a boiler drum, a heat exchanger, and steam generator tubing.

As used herein, the term "sorption" is meant to include, but is notlimited to, physical as well as chemical chemisorption effects andrefers to the ability of a substance to hold or concentrate gases, ions,solids including particulates or dissolved substances upon its surface.As used herein, the term "desorption" is meant to include the reverse ofsorption and refers to the evolution or liberation of a material from asolution or a substance.

As used herein, the term "controlling solid deposits" is meant toinclude, such as for example, but not limited to, solid depositinhibition, threshold precipitation inhibition, stabilization,dispersion, solubilization and/or particle size reduction of soliddeposits,; and the substantial prevention of solid deposit formation.

The term "effective amount" refers to that amount of a compositionnecessary to bring about a desired result such as, for example, theamount of volatile amine necessary for controlling and/or removing soliddeposits from a surface of a component of a steam generating system.Generally, for the method of the instant invention, the effective amountwill range such as, for example, from about 10 ppb to 50,000 ppb of thevolatile amine based on the total weight of the aqueous phase of thesteam generating system being treated, preferably from about 0.5 ppm to50 ppm, and most preferably from about 0.5 to 10 ppm.

As used herein, the term "pKa" is the symbol for the logarithm of thereciprocal of the acid dissociation constant of an electrolyte. Thereference temperature for pKa values is about 25° C. It will beunderstood by those skilled in the art that pKa values decline withincreasing temperature, and further, preferred amines will have a pKa athigher temperature equal to or greater than dimethylamine at saidtemperature. For example, the pKa of dimethylamine at about 250° C. isknown to be about 6.50 and at 25° C. is about 10.61.

As used herein, the term "passivation" refers to the formation of a filmwhich lowers the corrosion rate of the metallic surface which is beingtreated. "Passivation rate" refers to the time required to form aprotective film on a metallic surface.

The present invention provides a method for controlling and removingsolid deposits from a surface of at least one component of a steamgenerating system wherein the solid deposits are porous and are formedfrom an impurity introduced into the steam generating system-whichcomprises adding to an aqueous phase of the steam generating system aneffective amount of at least one volatile amine having a pKa valuegreater than about 10.61 and selected from the group consisting of analkyl amine, a cyclo alkyl amine, and derivatives thereof, convertingthe aqueous phase having the volatile amine to a steam phase having thevolatile amine, wherein the steam phase is selected from the groupconsisting of wet steam, saturated steam and superheated steam, exposingthe steam phase having the volatile amine to the surface of thecomponent laden with the solid deposits, wherein each of the soliddeposits has at least one functional site selected from the groupconsisting of (1) an acidic site to which an inorganic cation is sorbed,(2) a basic site to which an inorganic anion is sorbed, and (3)combinations thereof, for effecting selective sorption of the volatileamine by the solid deposit and displacing the inorganic cation, anion orcombinations thereof, and providing thermal cycling having a temperatureranging, for at least one cycle, from greater than or equal to about 0°C. to less than or equal to about 550° C. for effecting at least onecycle of sorption and desorption of the volatile amine wherein the rateof the desorption of said volatile amine exceeds the rate of diffusionof the volatile amine from the porous solid deposit for controlling andremoving the porous solid deposits from the surface of the component.Preferably, the method, as described herein, includes wherein the cycleof sorption is carried out at a temperature ranging from greater than orequal to about 0° C. to less than or equal to about 100° C., and whereinthe cycle of desorption is carried out at a temperature ranging fromgreater than or equal to about 100° C. to less than or equal to about550° C. More preferably, the method of the instant invention includeswherein the cycle of desorption is carried out by raising the desorptioncycle temperature above the sorption cycle temperature by greater thanor equal to an increment of about 100° C. Preferably, the volatile amineused in the instant invention is dimethylamine. Alternate volatileamines having a pKa value greater than about 10.61, which may be used inthe instant invention include, such as for example, but not limited to,mono-N-butylamine, monomethylamine, monoisopropylamine,tri-N-propylamine, monoethylamine, trimethylamine, triethylamine,diisobutylamine, 1,8 diaminooctane, 1,6 diaminohexane, 1,5diaminopentane, trimethyleneimine, di-N-propylamine, diethylamine,ethyl-N-butylamine, quinuclidene, tetramethyl-imino-bis-propylamine,pyrrolidine, di-N-butylamine, diisopropylamine,dimethylamino-propylamine, N-ethylcyclohexylamine, and 1,5diazabicyclo5.4.0undec-5-ene.

In a preferred embodiment of this invention, the method, as describedherein, includes wherein the components of the steam generating systemare selected from at least one of the group consisting of a turbine anda steam generator. It will be understood by those skilled in the artthat the surfaces of the components of the steam generating system aregenerally of a metallic character including, such as for example,metallic alloys.

It will be understood by those persons skilled in the art that thisinvention includes a method for exploiting the electrophoreticproperties of solid deposits formed from an impurity introduced into thesteam generating system, effecting the selective sorption of at leastone high pKa volatile amine and providing thermal cycling for removingthe solid deposits. It will be appreciated by those persons skilled inthe art that the physical step of thermal cycling of the presentinvention effects at least one cycle of sorption and desorption of thevolatile amine wherein the rate of desorption of the volatile amineexceeds the rate of diffusion of the volatile amine from the poroussolid, thus creating internal pressure, stress, and finally the spallingof the solid deposit. For example, it is believed that the sorption ofhigh pKa amines displaces inorganic cations such as, for example, Na⁺and K⁺, which are present at acidic centres on the solid deposit. Thisprovides a cleanup method to lower the corrosive impurity backgroundnear the metal surface of the component of the steam generating systemand within the steam cycle.

Removal of the solid deposit, from deposited impurities, eliminatessites for hideout of corrosive salts, both acidic and alkaline. It isimportant to note that the method of this invention for removing thesolid deposits does not require dissolution of the solid deposits, andtherefore, the instant method of removal includes the solid form andsorbed salts.

The instant method of solid deposit removal enhances the cleanup bydemineralization, filtration and blowdown systems of the steamgenerating system. It will be appreciated that the instant method ofremoval of sorbed inorganic salts minimizes their effect on the solutionchemistry and corrosion mechanisms, during the cleanup process. Further,the method of this invention can be practiced on-stream with the steamgenerating system operational or off-stream with the steam generatingsystem shut down. It will be appreciated that the method, as describedherein, includes employing the steam generating system in the shut downmode wherein the volatile amine is exposed to the surface of thecomponent laden with the solid deposits in an aqueous phase, in a steamphase, or combination thereof.

The applicants have found that employing the method of the presentinvention resulted in achieving a lower sodium concentration which is indirect contrast to the results achieved when the concentration ofconventional alkalizing amines such as, for example, ammonia,morpholine, hydrazine, or ethanolamine are raised in a steam generatingsystem.

When solids accumulate on the turbine or components comprising the steamgenerating system of a power plant, the heat transfer efficiency of theplant is decreased. This decrease in heat transfer efficiency translatesinto a lowering of the amount of megawatts which the system can produce.Elimination of the accumulated solids returns the heat transferefficiency, and therefore the megawatts of the plant, to the level itoperated at prior to the accumulation of the solids. In a most preferredembodiment of this invention, the method, as described herein, providesfor recovering substantially all megawatts of energy lost due to thesolid deposits accumulating on the turbine of the steam generatingsystem of a utility power station. In another preferred embodiment ofthe present invention, the method, as described herein, includesimproving the thermal efficiency of the steam generating system. Morespecifically, the present method improves steam cycle thermalperformance through control of deposited solids, from introducedimpurities, which inhibit heat transfer and/or distort critical designgeometries of the steam turbine component, thereby impacting steamutilization efficiency.

Another embodiment of the present invention provides a method asdescribed herein, including adding to the aqueous phase of the steamgenerating system an effective amount of at least one amine having a pKavalue less than 10.61 and an effective amount of at least one volatileamine having a pKa value greater than about 10.61.

It will be understood by those skilled in the art that the volatileamines employed in the method of the present invention, as describedherein, are water soluble or water dispersible.

EXAMPLES

The following examples demonstrate the invention in greater detail.These examples are not intended to limit the scope of the invention inany way.

Examples 1 and 2

Dimethylamine was introduced to the nuclear steam cycle, Example 1, andfossil steam cycle, Example 2, as a dilute aqueous solution, as setforth herein. DMA was fed to the aqueous phase of the system forExample 1. For Example 2, the main boiler bulk water was treated withdimethylamine to maintain the pH between about 9.6 and 9.8. Theconcentration of dimethylamine was varied, as set forth herein, toevaluate the efficacy for removal of deposited solids, resulting fromintroduced impurities.

Unconventional sampling and analysis methods were employed to elucidatethe form of materials removed. These methods included collection oftransported solids on submicron filters, arranged in series, and havingeffective ratings of about 0.45 microns to 0.015 microns. These filterswere subjected to surface examination techniques including scanningelectron microscopy (SEM), Electron Dispersive Spectroscopy (EDS) andelemental analysis by inductively coupled plasma (ICP) on acid dissolvedsamples.

Additional sampling included collection of transported solids throughparticulate filters, followed by cation exchange resins columns, andfinally through anion exchange resin columns. Since the electrophoreticproperties of the transported solids have positive and negative charges,passing the solids through both cationic and anionic exchange resinsallowed for differentiation of these solids based upon their acidic andbasic functionalities.

Additional sampling included scraping of deposits from the steam turbinefor Example 2, for the purpose of characterization. These results weredirectly compared to the composition of transported solids collectedduring the removal process. The steam turbine was visually inspectedbefore and after deposit removal to further verify the method.

Baseline samples, prior to dimethylamine addition, were conducted forExamples 1 and 2 to provide a benchmark for comparison. These resultswere taken in the presence of conventional amines not known to haveefficacy for removal of deposited solids from introduced impurities.More specifically, these treatments included employing the conventionalamines morpholine, hydrazine and ammonia for Example 1 and hydrazine,ammonia and phosphate for Example 2.

Example 1

Three separate phases of the nuclear plant demonstration includedbaseline studies, raising treatment levels to confirm the method andextended testing to optimize the treatment concentrations in a mixedamine system.

Comparison of ion exchange data indicating the amount of aluminumtransport for the feedwater (i.e. aqueous phase) and steam generatorblowdown, set forth in Table 1, reveals the reduction of aluminum belowdetection limits, after dimethylamine treatment. This data, from the ionexchange method, demonstrates the bifunctional properties of the solidhaving acidic functionality.

Steam generator blowdown data, set forth in Table 2, during initialapplication of dimethylamine reveals the abundance of various elements,exhibiting bifunctional properties. The cationic fraction being solubleand the anionic fraction being colloidal/particulate solids havingacidic functionality.

The EDS spectra from solids, as set forth in FIG. 1, collected duringinitial dimethylamine treatment revealed the composition of thedeposited solid and the sorbed salt species. This data reflected thatany sorbed monovalent species were cations such as, for example, sodiumand potassium, and indicated that the alumina silicates were formedunder alkaline conditions.

The elution of monovalent sodium, as set forth in FIG. 2, created aspike in concentration during initial treatments. It is important tonote that FIG. 2 shows that employing the method of this inventionresulted in the reduction in sodium to unprecedented levels not achievedby the background art. This was demonstrated further as dimethylaminewas raised to a higher concentration during the second phase of testing,as set forth in FIG. 3. Condensate polisher run time was extended fromthirty to sixty days during the demonstration of dimethylamine. Incontrast, raising the concentration of conventional amines, such asammonia, is known to increase sodium leakage from condensate polishersand to shorten the run time. Therefore, it will be appreciated by thosepersons skilled in the art that this invention represents a majortechnological breakthrough in steam cycle chemical treatments, havinglarge economic benefits.

The data for reduction of anions, as set forth in FIG. 4, particularlysulfate, reflected intervention of dimethylamine with retrograde saltssuch as calcium sulfate and magnesium sulfate, which deposit in steamcycles at high temperatures. The collection of the solid phase, as setforth in Table 2, of both calcium and magnesium before addition ofdimethylamine indicated that calcium and magnesium were below detectionlimits (i.e. not detectable), and that after the initial addition ofdimethylamine, both cationic and anionic functionality was present. Boththe metal sulfate and sulfide solids are known in the art to exhibitacidic functionalities. Data for the second phase of the demonstration,as set forth in FIG. 5, revealed further efficacy as dimethylamine wasraised to higher concentrations.

It will be appreciated that the results for Example 1, a 1150 megawattpressurized water reactor nuclear plant, clearly reveal that the methodof the present invention is a breakthrough in technology and thatdeposition of solids from introduced impurities can be effectivelycontrolled by the method of this invention. It will be appreciated thatcorrosion protection of critical plant systems is enhanced by reducingthe background concentration of corrosive salts as well as theirpresence when sorbed into solid acids and bases. Further, applicantsfound that employing the method of the present invention raised thesteam cycle thermal performance and increased the output of the highpressure steam turbine by about 0.4%.

Example 2

Three separate phases of the fossil plant demonstration include baselinedata collection prior to dimethylamine treatment, on-stream boilertreatment to reduce background levels of solids from introducedimpurities, and high pressure turbine cleanup including thermal cycling.It will be appreciated that thermal cycling includes plant cooldown andheatup to enhance the rate of cleanup.

Baseline data from turbine blade scrapings are shown in FIG. 6. Samples1 & 2 are from separate areas of the turbine blade but reflect similarcompositions by EDS analyses. These samples were then combined for XRDanalyses, as set forth in Table 3. Sample 3 was a filtered, high volume,steam drum location sample.

Comparison of Samples 1 & 2 vs. Sample 3 reflect predictable differencesin composition according to the relative volatility and solubility ofthe elements. Also, the turbine samples, 1 & 2, reflect greater basicityof the solid, although it was clearly bifunctional. The XRD analyses,Table 3, reveals a sample comprised primarily, of introduced impuritiesand high in alumina and silica. Compound identification included about45-56 percent sodium aluminum silicate (Na₂ O.Al₂ O₃.2.1 SiO₂) and about20-30 percent aluminum oxide hydroxide chloride (Al₁₇ O₁₆ (OH)₁₆ Cl₁₃).

Additional baseline studies include high volume integrated samples,on-stream, for the boiler drum, economizer inlet and superheatlocations. These and similar post injection samples were analyzed byICP. Comparison of results for the three distinct phases revealed steamtransport for baseline, boiler cleanup and turbine cleanup.

Five introduced impurities (Al, SiO₂, Ca, K, Na) are trended, FIGS.7-11, for the boiler drum sample. It should be noted that boiler drumblowdown was the primary means to extract impurities during all threephases. It will be appreciated that the collection of particulate,cation and anion fractions revealed the composition and electrophoreticproperties of solids removed from the boiler vs. the turbine.

FIG. 8 shows that employing the method of this invention resulted in aprompt reduction of electronegative silica and that much of the solidformed silica was removed equally as a cation and particulate. Solublecalcium was dramatically reduced and removal was by particulate andcation, as set forth in FIG. 9. The presence and removal of sodium as ananion was comparable during the first two phases but exceeded otherforms during the turbine phase, as set forth in FIG. 11. Both sodium andpotassium, see FIG. 10, were eluted by dimethylamine such that thesoluble fraction was increased.

Additional samples, during all phases, were analyzed by SEM and EDS tofurther reveal the composition of the solid deposits removed by theinstant invention employing dimethylamine. The economizer inlet samplesare presented for baseline, FIG. 12A, and for two turbine cleanupcycles, FIGS. 12B & 12C. The baseline sample did not reveal many of theelements as post treatment samples. Also, the post treatment boiler drumsample, FIG. 12D, contained an abundance of prismatic crystals ofcalcium phosphate.

It will be understood from this data that the removal of solids fromintroduced impurities employing the method of this invention was quitedramatic, thus reflecting the selectivity of these solids for volatileamines having a pKa value greater than about 10.61, and morespecifically, dimethylamine. The boiler cleanup phase increased steamtransport of solids and short term deposition at the high pressureturbine. The turbine cleanup phase resulted in a major improvement inunit output as shown in FIG. 13 of about 12 megawatts, while steam flowwas reduced, 8000 pounds per hour, below baseline conditions.

It will be appreciated that the method of this invention for controllingand removing steam cycle solid deposits from introduced impurities hasmany benefits and advantages over conventional amine treatments. Thebenefits include avoidance of conventional chemical cleaning, recoveryof unit output, improved heat rate, avoidance of turbine outages, andenhanced corrosion protection of the steam turbine. Further advantagesof the treatment include a low cost of application of the method of thisinvention without impact on plant availability.

The data for Examples 1 & 2 reflect the benefits and advantages ofemploying the method of this invention in both medium pressure (1000psi) and higher pressure (2500 psi) steam cycles. The lower pressuresystem, Example 1, is a 1150 megawatt pressurized water reactor powerplant, operated at or near saturated steam condition. The higherpressure system, Example 2, is a 400 megawatt, drum boiler design,fossil power plant, operated with superheat.

The preferred embodiment of the method of this invention employsdimethylamine as the volatile amine added to the aqueous phase of thesteam generating system. It will be appreciated by those skilled in theart that the efficacy and rate of deposit removal are affected byvolatility of the amine. Also, the application conditions vary fromsingle phase liquids, wet steam, saturated steam and superheated steam.For steam turbines, it was found that the distribution of volatileamines to the metal surface decreases as steam quality increases (wetsteam >>> saturated steam >>> superheated steam).

It will be further appreciated that conventional methods of cleaningsuch as, for example, but not limited to, chemical cleaning such as, forexample, foam cleaning, or mechanical cleaning such as, for example,water lancing or pressure pulse cleaning, can be augmented by employingthe method of the instant invention.

It was found while employing the method of this invention relative tothe thermal cycling step that the startup/shutdown modes of the utilitypower plant were optimum times for dimethylamine addition since lowersteam qualities increased surface activity of the volatile amine. Theaddition of the volatile amine to the steam generating system may be at,for example, the main boiler, auxiliary boiler or temporary boiler steamsupplies. For example, effective cleanup of a high pressure (2500 psi)turbine was demonstrated during normal startup evolutions. The mainboiler bulk water was treated with dimethylamine to maintain the pH (at25° C.) between about 9.6 and 9.8. Results included recovery of about 12megawatts electrical output and reduction of steam flow (8,000 poundsper hour) to improve unit heat rate.

It was found that employing the method of this invention at normal poweroperation that the rate of cleanup or efficacy was better for saturatedsteam conditions and low pressure turbines. Therefore, cleanup ofnuclear plant turbines was best accomplished at full power conditions.It was found that employing the method of this invention over a longerperiod of time was required for superheat steam conditions, such as highpressure fossil plants.

Further it was found while employing the method of this invention as toboilers or steam generators that the distribution of volatile amines tometal surfaces or crevices is reduced under steaming conditions.However, the distribution of the volatile amine was satisfactory toeffect cleanup of both a high pressure boiler and low pressure steamgenerator while at 100% power conditions. It will be appreciated thatthe method of the present invention for deposit removal may be employedoff-line, such as for example, as a soak or effecting a wet layup, asknown to those skilled in the art, using higher concentrations ofvolatile amines to enhance the rate of cleanup and coupled with thermalcycling. More specifically, this embodiment of the present inventionincludes raising the water level above the boiler/steam generator tubesand preferably above the steam separators, adding dimethylamine tomaintain about 0.5 to 10.0 ppm while maintaining temperature betweenabout 37° C. to 316° C., maintaining blowdown flow to remove solids andto promote circulation and mixing, and employing thermal cycling. It wasnoted that a partial heatup, such as, for example, about greater orequal to 100° C., was effective without reaching full operatingtemperatures.

Table 4 sets forth, for example purposes only, a partial list ofvolatile amines having a pKa value at 25° C. greater than about 10.61that may be employed in the method of the instant invention. It will beunderstood that the examples of volatile amines set forth in Table 4should not, however, be viewed as limiting the present invention in anyway.

Whereas particular embodiments of the instant invention have beendescribed for the purposes of illustration, it will be evident to thoseskilled in the art that numerous variations and details of the instantinvention may be made without departing from the instant invention asdefined in the appended claims.

                  TABLE 1                                                         ______________________________________                                        EXAMPLE 1                                                                     ALUMINUM TRANSPORT                                                            ION EXCHANGE METHOD                                                                   Anion       Cation      Total                                                 Concentration                                                                             Concentration                                                                             Concentration                                         (parts per billion)                                                                       (parts per billion)                                                                       (parts per billion)                           ______________________________________                                        FEEDWATER                                                                     Baseline                                                                              1.39        0.69        2.08                                          Day 22  1.0         0.49        1.49                                                                          (after DMA)                                   Day 46  ND          ND          ND                                            STEAM GENERATOR BLOWDOWN                                                      Baseline                                                                              1.62        1.16        2.78                                          Day 22  1.44        0.92        2.36                                                                          (after DMA)                                   Day 46  ND          ND          ND                                            ______________________________________                                         ND = Not Detectable                                                           DMA = Dimethylamine                                                      

                  TABLE 2                                                         ______________________________________                                        EXAMPLE 1                                                                     ION EXCHANGE METHOD-STEAM GENERATOR BLOWDOWN                                          Ca        Mg     Na       K    Al                                     ______________________________________                                        BASELINE DATA - BEFORE ADDITION OF DIMETHYLAMINE                              Cation  ND        ND     3.4      ND   1.16                                   Anion   ND        ND     0.4      ND   1.62                                   Total   ND        ND     3.8      ND   2.78                                   INITIAL ADDITION OF DIMETHYLAMINE                                             Cation  3.3       7.8    1.0      1.5  9.2                                    Anion   7.0       5.3    0.2      --   5.7                                    Total   10.3      13.1   1.2      1.5  14.9                                   ______________________________________                                         ND = Not Detectable                                                      

                  TABLE 3                                                         ______________________________________                                        EXAMPLE 2                                                                     TURBINE DEPOSIT ANALYSIS                                                      XRD METHOD WEIGHT %                                                                  Test 1 & 2 Above                                                       ______________________________________                                               Cl   0.020                                                                    F    0.099                                                                    SO.sub.4                                                                           0.023                                                                    PO.sub.4                                                                           1.96                                                                     SiO.sub.2                                                                          14.44                                                                    Na   3.49                                                                     Al   16.39                                                                    K    0.24                                                                     Ca   <0.001                                                                   Fe   2.90                                                                     Cu   3.11                                                                     Ni   0.05                                                                     Mn   0.02                                                                     Mg    0.0001                                                                  Pb   0.03                                                                     En   0.04                                                                     Co   0.007                                                             ______________________________________                                         XRD = XRay Diffraction                                                   

                  TABLE 4                                                         ______________________________________                                                  Amines              pKa                                             ______________________________________                                        DMA       Dimethylamine       10.61                                           MNBA      Mono-N-Butylamine   10.61                                           MMA       Monomethylamine     10.62                                           MIPA      Monoisopropylamine  10.63                                           TNPA      Tri-N-Propylamine   10.65                                           MEA       Monoethylamine      10.67                                           TMA       Trimethylamine      10.71                                           TEA       Triethylamine       10.74                                           DIBA      Diisobutylamine     10.82                                           DNPA      Di-N-Propylamine    10.90                                           DAP       1,5 Diaminopentane  10.915                                          HDA       1,6 Diaminohexane   10.93                                           DAO       1,8 Diaminooctane   10.937                                          DEA       Diethylamine        10.98                                           EBA       Ethyl-N-Butylamine  11.00                                           QUI       Quinuclidene        11.11                                           TMBPA     Tetramethyl-imino-bis-propylamine                                                                 11.20                                           PYR       Pyrrolidine         11.27                                           TME       Trimethyleneimine   11.29                                           DNBA      Di-N-Butylamine     11.31                                           DIPA      Diisopropylamine    11.50                                           DMAPA     Dimethylamino-propylamine                                                                         11.70                                           NECHA     N-Ethylcyclohexylamine                                                                            12.00                                           DBU       1,5-Diazabicyclo (5,4,0) Unde-5-ane                                                               13.40                                           ______________________________________                                         (pKa as defined at 25° C.)                                        

What is claimed is:
 1. A method for controlling and removing soliddeposits from a surface of at least one component of a steam generatingsystem laden with said solid deposits wherein said solid deposits areporous and are formed from an impurity introduced into said steamgenerating system and wherein said steam generating system producesmegawatts of energy, said method comprises:adding to an aqueous phase ofsaid steam generating system an effective amount of one or more volatileamines having a pKa value greater than about 10.61 at 25° C. andselected from the group consisting of an alkyl amine, a cyclo alkylamine, and derivatives thereof, to form an aqueous phase having said oneor more volatile amines, said effective amount being the amount of saidone or more volatile amines necessary for controlling and removing saidsolid deposits from said surface of at least one component of said steamgenerating system, said removing of solid deposits does not requiredissolution of said solid deposits; converting said aqueous phase havingsaid one or more volatile amines to a steam phase having said one ormore volatile amines, wherein said steam phase is selected from thegroup consisting of wet steam, saturated steam and superheated steam;exposing said steam phase having said one or more volatile amines tosaid surface of said component laden with said solid deposits, whereineach of said solid deposits has at least one functional site selectedfrom the group consisting of (1) an acidic site to which an inorganiccation is sorbed, (2) a basic site to which an inorganic anion issorbed, and (3) combinations thereof, for effecting selective sorptionof said one or more volatile amines by said solid deposits anddisplacing said inorganic cation, anion or combinations thereof; andproviding thermal cycling having a temperature ranging, for at least onecycle, from greater than or equal to about 0° C. to less than or equalto about 550° C. for effecting at least one cycle of sorption and onecycle of desorption of said one or more volatile amines wherein the rateof said desorption of said one or more volatile amines exceeds the rateof diffusion of said one or more volatile amines from said porous soliddeposit for controlling and removing said porous solid deposits fromsaid surface of said component.
 2. The method of claim 1 includingwherein said one or more volatile amines are selected from a groupconsisting of dimethylamine, mono-N-butylamine, monomethylamine,monoisopropylamine, tri-N-propylamine, monoethylamine, trimethylamine,triethylamine, diisobutylamine, 1,8 diaminooctane, 1,6 diaminohexane,1,5 diaminopentane, trimethyleneimine, di-N-propylamine, diethylamine,ethyl-N-butylamine, piperidine, quinuclidene,tetramethyl-imino-bis-propylamine, pyrrolidine, di-N-butylamine,diisopropylamine, dimethyl-amino-propylamine, N-ethylcyclohexylamine,and 1,5 diazabicyclo5.4.0undec-5-ene.
 3. The method of claim 1 includingwherein said one or more volatile amines are dimethylamine andpyrrolidine.
 4. The method of claim 1 including wherein said componentof said steam generating system is selected from at least one of thegroup consisting of a turbine and a steam generator.
 5. The method ofclaim 4 including wherein said removing of said solid deposits iscarried out on-stream with said steam generating system operational. 6.The method of claim 4 including wherein said removing of said soliddeposits is carried out off-stream with said steam generating systemshut down.
 7. The method of claim 4 wherein said controlling andremoving results in the steam generating system increasing itsgeneration of megawatts of energy to a level greater than said steamgenerating system was generating because of said solid depositsaccumulating on said component of said steam generating system.
 8. Themethod of claim 4 whereby said steam generating system has improvedthermal efficiency after removal of said solid deposits from saidcomponent.
 9. The method of claim 1 including adding to said aqueousphase of said steam generating system at least one amine having a pKavalue less than about 10.61.
 10. The method of claim 1 wherein saidsteam generating system has a sodium concentration, and said sodiumconcentration is decreased subsequent to said addition of said one ormore volatile amines.
 11. The method of claim 1 including carrying outsaid cycle of sorption at a temperature ranging from greater than orequal to 0° C. to less than or equal to about 100° C., and carrying outsaid cycle of desorption at a temperature ranging from greater than orequal to about 100° C. to less than or equal to about 550° C.
 12. Themethod of claim 1 including carrying out a cycle of desorption byraising a cycle of desorption temperature above said cycle of sorptiontemperature by greater than or equal to an increment of about 100° C.13. The method of claim 1 wherein said steam generating system resultsin enhanced corrosion protection.
 14. A method for controlling andremoving solid deposits from a surface of at least one component of asteam generating system laden with said solid deposits wherein saidsolid deposits are porous and are formed from an impurity introducedinto said steam generating system and wherein said steam generatingsystem produces megawatts of energy, said method comprises:adding to anaqueous phase of said steam generating system an effective amount of amixture of volatile amines having a pKa value greater than about 10.61at 25° C. and selected from the group consisting of an alkyl amine, acyclo alkyl amine, and derivatives thereof, to form an aqueous phasehaving said mixture of volatile amines, said effective amount being theamount of said mixture of volatile amines necessary for controlling andremoving said solid deposits from said surface of at least one componentof said steam generating system, said removing of solid deposits doesnot require dissolution of said solid deposits; converting said aqueousphase having said mixture of volatile amines to a steam phase havingsaid mixture of volatile amines, wherein said steam phase is selectedfrom the group consisting of wet steam, saturated steam and superheatedsteam; exposing said steam phase having said mixture of volatile aminesto said surface of said component laden with said solid deposits,wherein each of said solid deposits has at least one functional siteselected from the group consisting of (1) an acidic site to which aninorganic cation is sorbed, (2) a basic site to which an inorganic anionis sorbed, and (3) combinations thereof, for effecting selectivesorption of said mixture of volatile amines by said solid deposits anddisplacing said inorganic cation, anion or combinations thereof; andproviding thermal cycling having a temperature ranging, for at least onecycle, from greater than or equal to about 0° C. to less than or equalto about 550° C. for effecting at least one cycle of sorption and onecycle of desorption of said mixture of volatile amines wherein the rateof said desorption of said mixture of volatile amines exceeds the rateof diffusion of said mixture of volatile amines from said porous soliddeposit for controlling and removing said porous solid deposits fromsaid surface of said component.
 15. A method for controlling andremoving solid deposits from a surface of at least one component of asteam generating system laden with said solid deposits wherein saidsolid deposits are porous and are formed from an impurity introducedinto said steam generating system and wherein said steam generatingsystem produces megawatts of energy, said method comprises:adding to anaqueous phase of said steam generating system an effective amount of ablend of volatile amines having a pKa value greater than about 10.61 at25° C. and selected from the group consisting of an alkyl amine, a cycloalkyl amine, and derivatives thereof, to form an aqueous phase havingsaid blend of volatile amines, said effective amount being the amount ofsaid blend of volatile amines necessary for controlling and removingsaid solid deposits from said surface of at least one component of saidsteam generating system, said removing of solid deposits does notrequire dissolution of said solid deposits; converting said aqueousphase having said blend of volatile amines to a steam phase having saidblend of volatile amines, wherein said steam phase is selected from thegroup consisting of wet steam, saturated steam and superheated steam;exposing said steam phase having said blend of volatile amines to saidsurface of said component laden with said solid deposits, wherein eachof said solid deposits has at least one functional site selected fromthe group consisting of (1) an acidic site to which an inorganic cationis sorbed, (2) a basic site to which an inorganic anion is sorbed, and(3) combinations thereof, for effecting selective sorption of said blendof volatile amines by said solid deposits and displacing said inorganiccation, anion or combinations thereof; and providing thermal cyclinghaving a temperature ranging, for at least one cycle, from greater thanor equal to about 0° C. to less than or equal to about 550° C. foreffecting at least one cycle of sorption and one cycle of desorption ofsaid blend of volatile amines wherein the rate of said desorption ofsaid blend of volatile amines exceeds the rate of diffusion of saidblend of volatile amines from said porous solid deposit for controllingand removing said porous solid deposits from said surface of saidcomponent.
 16. A method for controlling and removing solid deposits froma surface of at least one component of a steam generating system ladenwith said solid deposits wherein said solid deposits are porous and areformed from an impurity introduced into said steam generating system andwherein said steam generating system produces megawatts of energy, saidmethod comprises:adding to an aqueous phase of said steam generatingsystem an effective amount of at least one volatile amine having a pKavalue greater than about 10.61 at 25° C. and selected from the groupconsisting of an alkyl amine, a cyclo alkyl amine, and derivativesthereof, to form an aqueous phase having said at least one volatileamine, said effective amount being the amount of said at least onevolatile amine necessary for controlling and removing said soliddeposits from said surface of at least one component of said steamgenerating system, said removing of solid deposits does not requiredissolution of said solid deposits; converting said aqueous phase havingsaid at least one volatile amine to a steam phase having said at leastone volatile amine, wherein said steam phase is selected from the groupconsisting of wet steam, saturated steam and superheated steam; exposingsaid steam phase having said at least one volatile amine to said surfaceof said component laden with said solid deposits, wherein each of saidsolid deposits has at least one functional site selected from the groupconsisting of (1) an acidic site to which an inorganic cation is sorbed,(2) a basic site to which an inorganic anion is sorbed, and (3)combinations thereof, for effecting selective sorption of said at leastone volatile amine by said solid deposits and displacing said inorganiccation, anion or combinations thereof; and providing thermal cyclinghaving a temperature ranging, for at least one cycle, from greater thanor equal to about 0° C. to less than or equal to about 550° C. foreffecting at least one cycle of sorption and one cycle of desorption ofsaid at least one volatile amine wherein the rate of said desorption ofsaid at least one volatile amine exceeds the rate of diffusion of saidat least one volatile amine from said porous solid deposit forcontrolling and removing said porous solid deposits from said surface ofsaid component, and wherein enhanced corrosion protection results insaid steam generating system.
 17. The method of claim 16 includingwherein said at least one volatile amine is selected from a groupconsisting of dimethylamine, mono-N-butylamine, monomethylamine,monoisopropylamine, tri-N-propylamine, monoethylamine, trimethylamine,triethylamine, diisobutylamine, 1,8 diaminooctane, 1,6 diaminohexane,1,5 diaminopentane, trimethyleneimine, di-N-propylamine, diethylamine,ethyl-N-butylamine, piperidine, quinuclidene,tetramethyl-imino-bis-propylamine, pyrrolidine, di-N-butylamine,diisopropylamine, dimethyl-amino-propylamine, N-ethylcyclohexylamine,and 1,5 diazabicyclo5.4.0undec-5-ene.
 18. The method of claim 16including wherein said at least one volatile amine is dimethylamine andpyrrolidine.